I have heard that at some point training can actually become detrimental. I just wanted to ask if anybody has had experience with this, and when do you know if you are over training to the point where it becomes detrimental?

There are several things that could happen: One is injury. Another is that your body doesn't have enough time to recover in between training sessions. After you stress your muscles, they need time to rebuild. A third possibility is burn-out: you don't want to train so hard that it isn't fun anymore. I have experienced all three! I don't know if there is a formula to tell you when you are over-training, but I know you need to listen to your body.

I'll try to put some numbers behind what is considered a good rest period between different types of exercises but really what it comes down to is listening to your body.

DOMS Delayed Onset Muscle Soreness (the ache and stiffness you feel in your muscles between 24 and 72 hours after strength training) is "OK" and considered a normal symptom of effective muscle training.

Joint, skeletal and tendon pain is not "OK" and a sign of over training/injury depending on the severity.

Any strength training (anaerobic) (reps of less then 15) should be followed with 3 to 4 days of rest for the muscle group trained.

Any endurance training (Aerobic) has a much shorter rest period and is very individual specific. For example when training for long distance running, I was able to increase endurance by 10% every 48 hours.

There are some few people who, through smart training tactics and good genetics, can sustain inordinate amounts of training. Patxi is a great example of that kind of person. You might hear some call people like that "mutants".

Those people have also generally been involved in other athletic training or climbing for most of their lives. Don't look to the mutants for training tips!